The present invention relates to the field of aerosols, in general, and to aerosol coating compositions, in particular.
The need to increase the night-time or low light visibility of objects, such as signs, has plagued mankind for centuries. For many apparent reasons, the need to read signs, such as highway roadsigns, or to be made aware of certain potentially dangerous conditions, is more critical at night than during daylight hours. Accordingly, reflectorized coatings or surfaces have been developed for the purpose of increasing the night-time or low-light visibility of objects. Such reflectorized surfaces then act to reflect or return incident light, as from an automobile headlight, back generally toward the source of such light. Unfortunately, the production of reflectorized signs or objects generally has required special processing techniques which are commercially performed only by a limited number of establishments. The costs for such commercially produced objects have been relatively high and essentially prohibitive when only a limited quantity of specialized signs or the like are desired.
A need therefore has existed for a means to render common objects, such as signs, reflective, without great expense. U.S. Pat. No. 2,354,018 is directed toward what was believed to be one possible solution to such a need. In that patent there is disclosed a light reflective beaded sheet material, designed to be adhesively affixed to objects, including pre-existing signs, and the like. However, the sheet material incorporates either a pigmented sizing film or a reflector sizing coat in the sheet material which then obscures any underlying printing or the like on the substrate, requiring then careful cutting of lettering into or from the sheet material, to construct any desired sign. That solution is not believed to have found acceptance, perhaps due to the inability to form weather-resistant adhesive bonds to the underlying substrate, or perhaps due to the cumbersome need to carefully cut the material into the desired shapes and patterns. More likely, the lack of convenience of such an approach has been responsible for its lack of acceptance.
Another factor of concern in this field is the ability to quickly increase the night or low-light visibility of an object, as may be necessary in an emergency situation. In the past, emergency situations, such as the need to warn of a stalled car or other object on or near a highway, have been addressed by placing mobile, reflectorized objects near the obstruction. Such an approach is unsatisfactory, however, because it does not highlight the obstruction itself and in fact tends to attract a driver's attention to the reflectorized object and away from the obstruction of concern.
It is clear that a need also has existed for a means to increase the night-time or low light visibility of an object in a reasonably rapid manner, without distracting an observer's attention away from the object itself. U.S. Pat. No. 3,099,637 is concerned with certain compositions which evidently were believed to be useful for converting ordinary reflective surfaces into reflex-reflecting ones. The compositions contain glass beads having diameters preferably between about 15 and 60 microns and are said to be sprayable. No mention is made of application of such compositions via aerosol means.
The compositions of the '637 patent have not found general acceptance, perhaps at least in part due to the lack of an easy means to apply the same. The patent suggests application by means of classical brushing technique, which is cumbersome and not readily applicable in emergency situations. Further, it is difficult to achieve, through brushing, a thin, uniform surface layer which will not be readily noticed in daylight or normal ambient light conditions.
Others also have suggested the application of various types of glass beads, for purposes of increasing visibility of objects or areas. For example, U.S. Pat. No. 2,574,971 concerns certain highway marking paint which contains glass beads. The paint is said to be sprayable, assumedly through the use of typical spray gun technology, due to its early date (1951). RE 30,892 is concerned with a composition used to retro-reflectively treat fabrics, the composition including transparent microspheres and specular reflective means underlying the microspheres to make the microspheres retro-reflective. As a general principle, for nonaerosol applications of glass beads, those skilled in that art have recognized that larger glass beads afford better reflectivity than smaller glass beads.
Aerosol means of application of certain small-sized glass beads has been suggested in the art. In U.S. Pat. No. 2,963,378, there is suggested the use of glass beads having an optimum size, in accordance with that reference, of 10 to 50 microns in diameter for certain formulations which include aerosols. The beads are reflectorized by a metallic coating over approximately one-half of their surface. The formulations are purportedly for use in providing coatings for highway signs and markers that have long-range visibility when viewed at night.
U.S. Pat. No. 3,228,897 relates to certain coating compositions containing glass beads which are stated to be capable of application by various techniques, including spray methods. The patent contains one example of a composition indicated to be of use in an aerosol container, although no actual example of an aerosol formulation is present. The beads are indicated to have a particle size of about 25 to about 75 microns, but only glass beads having particle sizes in the 20-45 micron size range are actually used in the working examples. Further, the beads are applied in combination with a reflective metallic pigment which acts to form reflective back surfaces for the glass beads.
Despite the fact that glass bead aerosol formulations are suggested in the foregoing references which have been in existence for decades, no actual commercial use of such formulations is known.
Of more recent era, U.S. Pat. No. 4,329,393 discusses the use of hemispherically coated glass beads having a particle size in the range of 10 to 60 microns, but with a particle size of 10 to 50 microns for aerosol application, for the purpose of speeding recognition of the location of certain microparticles or taggants on a labeled object. The beads are used to reflectorize and thus highlight the location of the microtaggants, upon being illuminated with an incident beam of light. It is clear that the apparent cumulative teaching of the foregoing prior art is that aerosol formulations containing glass beads with a particle size of about 10 to about 60 microns, preferably about 10 or 20 to about 45 microns, can be used in aerosol coating compositions to reflectorize a substrate. Also in accordance with the art, the beads should have some metallic reflector in back of or coated onto such particles. However, the fact remains that even though much of the art in this area has been in existence for decades, no such compositions are believed to have found commercial acceptance and none are believed to be currently commercially available.
The present invention is directed toward the still unsatisfied need for a convenient and speedy means for increasing the reflectivity of an object or substrate, such as an aerosol composition.